Percutaneous transluminal coronary angioplasty (PTCA) is a common procedure for treating heart disease. A problem associated with the PTCA includes the formation of intimal flaps or torn arterial linings which can collapse and occlude the conduit after the balloon is deflated. Moreover, thrombosis and restenosis of the artery may develop over several months after the procedure, which may require another angioplasty procedure or a surgical by-pass operation. To reduce the partial or total occlusion of the artery by the collapse of arterial lining, and to reduce the chance of the development of thrombosis and restenosis, a stent may be implanted in the lumen to maintain the vascular patency.
Stents are used not only as a mechanical intervention but also as a vehicle for providing biological therapy. As a mechanical intervention, stents act as scaffoldings, functioning to physically hold open and, if desired, to expand the wall of the passageway. Biological therapy can be achieved by medicating the stents, in particular by using drug-eluting stents, DESs. DESs can provide local administration of a therapeutic substance at the specific site in an patient's body. This can result in fewer and less severe side effects and more favorable overall results.
The early use of coronary stents to improve the long-term patency of an artery post-angioplasty was, however, complicated by a high incidence of subacute thrombosis (SAT) (R.A. Schatz et al., Circulation 1991, 83: 148-161). Despite improved pharmacological control of SAT, the potential for stent occlusion remains a serious problem. In addition, with the advent of DESs a new problem arose: late stent thrombosis, the forming of blood clots long after the stent is in place. It was deduced that the formation of blood clots was most likely due to delayed healing which was postulated to be a side-effect of the use of cytostatic drugs.
Delayed healing and polymer degradation have also been associated with stent malapposition, and hypersensitivity reactions.
What is needed is an implantable medical device that has improved hemocompatibility and/or prohealing properties to amelioreate, if not eliminate, subacute thrombosis, late stent thrombosis and other problems associated with delayed healing. The current invention provides such implantable medical devices.